Grant: Collaborative Health Research Projects (NSERC partnered)

Current localized treatments of benign bone tumours in children suffer from significant side effects including the invasiveness of surgical removal with bone reconstruction, and the associated risk of developing secondary malignancy from high-dose radiation therapy. Magnetic resonance guided focused ultrasound (MRgFUS) is a noninvasive thermo-therapy that has recently been clinically approved in Canada for uterine fibroid ablation and is currently in clinical trials in Canada for palliative management of bone metastasis pain. It is also showing promise as an effective local treatment, when combined with chemotherapy, for malignancies throughout the body. The principle therapeutic technique underlying MRgFUS is the noninvasive focusing of high intensity ultrasound energy to induce thermal necrosis in a target volume as small as a rice kernel. Localized temperature elevations in the target tissue can be monitored noninvasively and in real time inside a clinical magnetic resonance imaging (MRI) scanner. However, conventional MRI thermometry is limited to water-based soft tissues, such as muscle, and temperature is not measured in cortical bone and fat-based tissues such as bone marrow, preventing its use as a primary local treatment for bone tumours. Since many bone tumours grow within both the cortical bone and bone marrow, accurate assessment of temperature in both of these tissues during treatment is required to ensure adequate thermal necrosis. We hypothesize that bone marrow temperature can be measured accurately by quantifying the change in magnetic relaxation time of the fat-rich bone marrow during heating, and that the temperature distribution across the cortical bone can be calculated from the surrounding measured temperatures in the muscle and bone marrow. This method will enable the safe application of MRgFUS for local treatments of benign bone neoplasms and will improve treatment and quality of life for paediatric bone tumour patients.